Familiarity
The Key to Understanding Spellwork

by Paul Dionne

Why didn't Quirrell just Summon the Philosopher's Stone
to him (PS17)?
He probably couldn't. Here's why:

Magic requires many elements, but a prime one is familiarity.
That is why most spells are line-of-sight. The wizard must see what
it is in order to charm/curse it. This has been said many times.
[
An excellent example is when Quirrell and Snape
were both casting spells on Harry in the Quidditch match
(PS11). As
Hermione pointed out later, it was imperative that a caster maintain
eye contact. -- ed.
]

But then how
could Harry use an Accio spell to fetch his Firebolt when it wasn't within
his sight? Well, two points. 1) Harry knows his Firebolt inside and out,
he is very 'in tune' with it so to speak; and 2) he knows exactly where
it is. Now I would suppose that, even if he didn't know where it is, his
familiarity with it would suffice (if he were powerful enough).

I suspect that
such magics have three levels of power: Any wizard worth his salt can Accio
a visible object, a more powerful wizard is needed to Accio a familiar
and location-known object, but not visible, and only the most powerful
can Accio an object on familiarity alone.

Now Quirrell
did not know what the Philosopher's Stone looked like (it's been locked
up for ages), and I think more than just *seeing it* would equal familiarity
for an object that was not in line-of-site. And he does not *absolutely
know* where it is. So he loses on all three accounts.

But there are a few possible snags to this theory, specifically with
regards to the Accio spell. Mrs. Weasley uses it repeatedly to remove things
from Fred and George's clothing
(GF6,
things that she wasn't sure what or where they were. How can this work?

she saw them put something in their pockets (not likely)

she obviously sees that "something" is in their pockets.
The pockets themselves are visible, they're bulging out or
something. There has to be something there, and she knows it (more likely)

And frankly,we have to consider the distinct possibility that she was all
too familiar with the sort of things
Fred and George likely had in their
pockets. This very well might not have been the first time she'd
been through this scenario with the two of them.

But even if she didn't know exactly what they had,
she probably could see that they had something,
and that would be enough. Familiarity in this case means
simply knowing for certain that something is there.

For example,
if a wizard saw a tablecloth over an obvious object underneath,
that person could Accio it into his or her hand. Of course, this
could be verrrrry dangerous. It could be a bowling ball
with teeth or something.

It would be different if there were an object in a tablecloth in
a room not in view. Then there's nothing there as far as the person
knows, hence no Accio.

So then what about the Aqualung Harry briefly considered Accio-ing
from a nearby Muggle village for the
second task
(GF26)?
The idea was shot down in short order, so we didn't hear it
planned out in detail, but it seems likely that Harry would have
had to make a trek into that town ahead of time and figure out
where such an unusual object might be located and make himself
familiar with it. If he didn't it would be impossible to have
Accio-ed it. Familiarity is key.

I think this can apply to a Portkey and other spells as well.
You can't create a Portkey to somewhere you do not know, and
you might not even be able to
Apparate
to a place you do not know. How did the
Death EatersApparate to
Voldemort in the graveyard?
VoldemortVoldemort
sent up a "flare" with the
Dark Mark tattoo, a sort of Death Eater homing beacon.